• Frequency range

  • Ensure that the amplifier’s range encompasses the frequency you’re targeting (433 MHz in this case)

• Gain

  • Usually power gains are due to voltage increases, but may sometimes be accompanied by current increases. Check maximum ratings of other equipment to make sure you don’t fry the chip

• Bandwidth flatness

  • You generally want the gain across the bandwidth you are using to be constant
  • Higher frequencies result in lower gain usually
  • There may sometimes be lower limits as well, but usually not

  

• Slew Rate (SR)

  • Defines the speed at which the output can change, usually defined in V/s
  • Max slew rate of your input is $\frac{d}{dt}Asin(\omega t)$ at $t=0$
    • Simplifies to $slew rate = 2A\pi F$

• Noise Figure (NF)

  • Measure of electrical noise produced by amplifier components
  • NF = 10log(SNR in/SNR out)
  • SNR = Signal/Noise ratio
  • 0 dB NF ⇒ no noise is added
  • Anything less than 3dB is good, 2dB is ideal

• Total Harmonic Distortion (THD) or THD+N (plus Noise)

  • Combination of harmonic and noise interferences causing decrease in output SNR
  • Lower number = better

• Impedance

  • 50 ohms everywhere

• Output power

  • Max power that can be produced on a 50 ohm load at the highest supply voltage
  • Usually given in dBm, typically between 12-28 dBm

• Third-order intercept (IP3)

  • Quantifies intermodulation distortion
  • Higher IP3 value indicates better linearity and performance of the amplifier

• P1dB (1 dB Compression Point)

  • As you increase power to an amplifier, its output power also increases linearly, up to a point at which it begins compressing due to distortion/clipping at max power → P1DB is the output power for which the theoretical output should be 1dB higher if there were no compression
  • In other words, there is a maximum output power around which a power amplifier begins to saturate to a constant level → P1dB characterizes this level
  • Exceeding saturation leads to slight clipping of the wave, and more importantly produces harmonics that interfere with the signal. Therefore, it is undesirable to have an amplifier whose gain may cause your output to exceed your P1dB based on your input.
    • That being said, PAs are also most efficient closest to their P1dB values [more information needed on why], and so you ideally want to pick one where your maximum input power multiplied by your gain gives you an output power close to P1dB

• Solid-state technology: usually SiGe > GaAs
• DC input power:
  • Should be either 3.3V or 5V voltage to be compatible with our satellite
  • Lower amperage draw is better
  • DC input is often called bias or supply voltage, and is often fed into the RF out pin of an amplifier through an inductor
• Temperature range
  • Should meet regular environmental requirements
• Power Added Efficiency (PAE)
  • Percentage between 0 to 100 defined by $PAE=\frac{P_{out}-P_{in}}{P_{DC}}=P_{in}(10^{\frac{G}{10}}-1)/P_{DC}$, where $P_{in}$ is the input RF power, $P_{out}$ is the output RF power, and $P_{DC}$ is the input to the IC

Criteria for Custom Transceiver PA

1. Mandatory: P1dB/max output power between 25-31dBm (0.316W to 1.26W)
2. Mandatory: Supports 433 MHz frequency or 902MHz
3. Guideline**:** Operating voltage must include 3.3V or 5V
4. Important: Low power consumption is important (i.e low current draw). Aim for <1W operating power (i.e. current times voltage less than 1W)